The production of lumber often involves the use of automated grading systems that use image scanning and processing techniques to identify grade and other characteristics of lumber travelling longitudinally over a conveyor. Once a piece of lumber has been graded, it may be marked with a stamp, ink, or another physical mark to display the grade and sometimes other attributes of each piece of lumber. Typically, this is done by spraying visible colored ink representing various grades onto the lumber.
The lumber is generally transported on lugged or unlugged chains transversely through a mill. Grade printers may be located downstream of a board trimmer to apply a stamp to each board. For example, a lumber grader might call for grade #2-8′ on a near end of a board and grade #3-10′ on a far end of the board. When this happens, a trimmer will cut an eighteen foot board in two pieces at approximately an eight foot position. Once these different grade boards are on different lugs, they may be stamped with the appropriate grade stamps.